A blockchain is a public database that is updated and shared across many computers. Think of it as an excel spreadsheet across tons of devices; the only difference is that the file must continuously be up to date on each device.The blockchain block refers to the data stored; this can be any dataset, such as information about a user. Consider the following:

    This is a block of data! Super simple.

    A blockchain chain refers to the relation of one block to another.Above are multiple blocks that relate to one another via the blockNumber and parentBlock fields to create the chain. You can also see that each block has a parent block beside the genesis block! Now we have a blockchain!- Cryptocurrencies are built on blockchains as a continuously updated record of "who holds what."

    - The continuously updated list of records is also referred to as a "Distributed ledger." 

    Centralized Ledger vs. Distributed Ledger

    Distributed Ledger:  
    • A shared record of account, available for anyone to download without permission.

    • Distributed means the ownership of the network is shared by participants making there no central point of authority.

    • Distributed = available for anyone to download and verify without permission

    • Ledger = Recorded list or database

    Linked Blocks

    - One key difference between a typical database and a blockchain is the way the data is structured. A blockchain collects information together in groups, also known as blocks, that hold sets of information. Blocks have certain storage capacities and, when filled, are chained onto the previously filled block, forming a chain of data known as the “blockchain.” All new information that follows that freshly added block is compiled into a newly formed block that will then also be added to the chain once filled.- The history of records is split into linked blocks and then secured using Cryptography.- When a block is filled, it is set in stone and becomes a part of this timeline.- Each block in the chain is given an exact timestamp when it is added to the chain.

    What's in a Block?

    • Each block contains 3 primary items:1) Data:

    • The initiator of the transaction

    • Timestamp

    • Recipient of the transaction

    2) Hash

    • identity of a block generated by cryptography

    3) Previous hash

    • contains the proof of the previous message


    Cryptography is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it.
    The Bitcoin Blockchain: Proof of Work

    The blockchain is designed to reveal tampering in real-time, demonstrating unhackable properties. When a block is attacked/tampered with, the whole system is alerted through consensus, which results in the block being rejected unless the consensus accepts those changes. An attack (bribe or fraud) is basically an attempt to change the system's protocol rules by influencing consensus. The Proof of work protocol is an application of cryptography used by Bitcoin. Ethereum developers are working on a proof of stake cryptographic application.